The regress argument Philo presents misunderstands the nature of the First Cause. The cosmological argument does not claim that every cause must have a cause, but that contingent beings require a necessary being as their ultimate explanation. The regress of contingent causes cannot proceed to infinity; there must be a first cause that is itself uncaused, not contingent but necessary, not needing explanation because it exists by the necessity of its own nature. This is God—ipsum esse subsistens, subsistent being itself. God does not need a cause because God is not a contingent being but the necessary ground of all contingent reality. To ask 'what caused God?' is to misunderstand the ontological distinction between necessary and contingent being.

The question 'who designed the designer?' only arises if we think of God as a contingent being like the universe. But God, in classical theism, is a necessarily existent being. God exists in all possible worlds and does not require a cause or explanation beyond Himself. The cosmological argument, properly understood, argues from contingent beings to a necessary being, not from complex beings to an even more complex being. Necessary existence is part of the concept of God, so asking what caused God is like asking what makes a bachelor unmarried—it reveals a misunderstanding of the concept. The regress terminates in God because God is metaphysically ultimate, the explanation of all contingent reality.

The question of what explains God's existence is answered by recognizing that God is a necessary being—God exists in virtue of God's own nature, not because of some external cause. But we must be careful about the concept of necessity. God's existence is not logically necessary (the concept is coherent but the existence is not entailed by logic alone). Rather, God's existence is metaphysically necessary—God exists in all metaphysically possible worlds. The explanation for God's existence is that a person of infinite power, knowledge, and goodness is the simplest possible explanation of everything else. Simplicity is a criterion of good explanation, and God is the ultimate in simplicity—one being with unlimited attributes.

This is exactly right. The theist's answer to complexity is to postulate something even more complex, then arbitrarily declare that this complex designer needs no explanation. If God can exist without a cause, why can't the universe? Theists engage in special pleading when they insist that everything needs an explanation except God. The scientific approach is to explain complex things in terms of simpler things—and ultimately, the laws of physics and initial conditions may be all the explanation we need. Even if we don't yet have a complete explanation for the universe's existence, postulating God just pushes the problem back a step without actually solving it. It's an explanatory dead end.